Hmm.. I've been trying to decode the QR Code for the extra levels (using the one from Nintendo Life), but no luck so far. Has anyone else tried? Anyone interested? If you look at the QR code, you can see some "miniature versions" of the centering squares (a dot with a white border with a black border). Reading the QR code with a conventional scanner reveals tons of random unreadable characters. Same result if I remove the miniature versions of the "centering squares".

No. The most applications available is capable to encode only standard text or url, but not raw binary data which is used in Pyramids ws well as Mii QR codes.
Anyway Pyramids levels seems to be protected somehow, maybe even ciphered. One bit change of raw data makes unusable QR code for Pyramids. More levels is needed for complete analysis.

there's an interview with the coders discussing the game and how they want to work with the community to make QR levels

also, after finding this post last night and getting curious i found their facebook page https://www.facebook.com/EnjoyGaming where they have in their pictures section some levels and the corresponding QR code underneath.